Sonar may be used to detect surfaces such as the bottom of a body of water in a bathymetry operation. For example, fishfinding sonar systems for watercraft often track the bottom so that the depth to which the fishfinding sounders ping can be controlled so that the bottom is always in range of the sounders. In some circumstances, conventional bottom finding systems can provide erroneous bottom detections such as in areas of increased noise in the sonar data. Thus, there is a need for improved surface detection sonar systems.